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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.collect;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import com.google.common.annotations.GwtCompatible;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.io.Serializable;<a name="line.21"></a>
<span class="sourceLineNo">022</span><a name="line.22"></a>
<span class="sourceLineNo">023</span>/**<a name="line.23"></a>
<span class="sourceLineNo">024</span> * An abstract base class for implementing the &lt;a<a name="line.24"></a>
<span class="sourceLineNo">025</span> * href="http://en.wikipedia.org/wiki/Decorator_pattern"&gt;decorator pattern&lt;/a&gt;.<a name="line.25"></a>
<span class="sourceLineNo">026</span> * The {@link #delegate()} method must be overridden to return the instance<a name="line.26"></a>
<span class="sourceLineNo">027</span> * being decorated.<a name="line.27"></a>
<span class="sourceLineNo">028</span> *<a name="line.28"></a>
<span class="sourceLineNo">029</span> * &lt;p&gt;This class does &lt;i&gt;not&lt;/i&gt; forward the {@code hashCode} and {@code equals}<a name="line.29"></a>
<span class="sourceLineNo">030</span> * methods through to the backing object, but relies on {@code Object}'s<a name="line.30"></a>
<span class="sourceLineNo">031</span> * implementation. This is necessary to preserve the symmetry of {@code equals}.<a name="line.31"></a>
<span class="sourceLineNo">032</span> * Custom definitions of equality are usually based on an interface, such as<a name="line.32"></a>
<span class="sourceLineNo">033</span> * {@code Set} or {@code List}, so that the implementation of {@code equals} can<a name="line.33"></a>
<span class="sourceLineNo">034</span> * cast the object being tested for equality to the custom interface. {@code<a name="line.34"></a>
<span class="sourceLineNo">035</span> * ForwardingObject} implements no such custom interfaces directly; they<a name="line.35"></a>
<span class="sourceLineNo">036</span> * are implemented only in subclasses. Therefore, forwarding {@code equals}<a name="line.36"></a>
<span class="sourceLineNo">037</span> * would break symmetry, as the forwarding object might consider itself equal to<a name="line.37"></a>
<span class="sourceLineNo">038</span> * the object being tested, but the reverse could not be true. This behavior is<a name="line.38"></a>
<span class="sourceLineNo">039</span> * consistent with the JDK's collection wrappers, such as<a name="line.39"></a>
<span class="sourceLineNo">040</span> * {@link java.util.Collections#unmodifiableCollection}. Use an<a name="line.40"></a>
<span class="sourceLineNo">041</span> * interface-specific subclass of {@code ForwardingObject}, such as {@link<a name="line.41"></a>
<span class="sourceLineNo">042</span> * ForwardingList}, to preserve equality behavior, or override {@code equals}<a name="line.42"></a>
<span class="sourceLineNo">043</span> * directly.<a name="line.43"></a>
<span class="sourceLineNo">044</span> *<a name="line.44"></a>
<span class="sourceLineNo">045</span> * &lt;p&gt;The {@code toString} method is forwarded to the delegate. Although this<a name="line.45"></a>
<span class="sourceLineNo">046</span> * class does not implement {@link Serializable}, a serializable subclass may be<a name="line.46"></a>
<span class="sourceLineNo">047</span> * created since this class has a parameter-less constructor.<a name="line.47"></a>
<span class="sourceLineNo">048</span> *<a name="line.48"></a>
<span class="sourceLineNo">049</span> * @author Mike Bostock<a name="line.49"></a>
<span class="sourceLineNo">050</span> * @since 2.0 (imported from Google Collections Library)<a name="line.50"></a>
<span class="sourceLineNo">051</span> */<a name="line.51"></a>
<span class="sourceLineNo">052</span>@GwtCompatible<a name="line.52"></a>
<span class="sourceLineNo">053</span>public abstract class ForwardingObject {<a name="line.53"></a>
<span class="sourceLineNo">054</span><a name="line.54"></a>
<span class="sourceLineNo">055</span>  /** Constructor for use by subclasses. */<a name="line.55"></a>
<span class="sourceLineNo">056</span>  protected ForwardingObject() {}<a name="line.56"></a>
<span class="sourceLineNo">057</span><a name="line.57"></a>
<span class="sourceLineNo">058</span>  /**<a name="line.58"></a>
<span class="sourceLineNo">059</span>   * Returns the backing delegate instance that methods are forwarded to.<a name="line.59"></a>
<span class="sourceLineNo">060</span>   * Abstract subclasses generally override this method with an abstract method<a name="line.60"></a>
<span class="sourceLineNo">061</span>   * that has a more specific return type, such as {@link<a name="line.61"></a>
<span class="sourceLineNo">062</span>   * ForwardingSet#delegate}. Concrete subclasses override this method to supply<a name="line.62"></a>
<span class="sourceLineNo">063</span>   * the instance being decorated.<a name="line.63"></a>
<span class="sourceLineNo">064</span>   */<a name="line.64"></a>
<span class="sourceLineNo">065</span>  protected abstract Object delegate();<a name="line.65"></a>
<span class="sourceLineNo">066</span><a name="line.66"></a>
<span class="sourceLineNo">067</span>  /**<a name="line.67"></a>
<span class="sourceLineNo">068</span>   * Returns the string representation generated by the delegate's<a name="line.68"></a>
<span class="sourceLineNo">069</span>   * {@code toString} method.<a name="line.69"></a>
<span class="sourceLineNo">070</span>   */<a name="line.70"></a>
<span class="sourceLineNo">071</span>  @Override public String toString() {<a name="line.71"></a>
<span class="sourceLineNo">072</span>    return delegate().toString();<a name="line.72"></a>
<span class="sourceLineNo">073</span>  }<a name="line.73"></a>
<span class="sourceLineNo">074</span><a name="line.74"></a>
<span class="sourceLineNo">075</span>  /* No equals or hashCode. See class comments for details. */<a name="line.75"></a>
<span class="sourceLineNo">076</span>}<a name="line.76"></a>




























































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